Method of removing manganese oxide deposits

ABSTRACT

A METHOD OF REMOVING MANGANESE CONTAINING DEPOSITS FORMED ON THE SURFACES OF JET ENGINES FROM BURNING FUEL CONTAINING A CYCLOPENTADIENYL MANGANESE TRICARBONYL AS A SMOKE REDUCER, BY TREATING THE CEPOSIT COATED SURFACES WITH AN AQUEOUS SOLUTION OF HYDROXYLAMINE SALT. HYDROXLYAMINE SALTS OF CARBOXYLIC ACIDS ARE EXAMPLES OF USEFUL COMPOUNDS.

United States Patent US. or. 134-3 Claims A method of removing manganesecontaining deposits formed on the surfaces of jet engines from burningfuel containig a cyclopentadienyl manganese tricarbonyl as a smokereducer, by treating the deposit coated surfaces with an aqueoussolution of hydroxylamine salt.

Hydroxlyamine salts of carboxylic acids are examples of usefulcompounds.

CROSS REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part of Ser. No. 692,321, filed Dec. 21, 1967, nowabandoned.

BACKGROUND OF THE INVENTION Smoke produced during the operation of adistillate fuel burning engine, such as a jet engine, is undesirable. Itcontributes to air pollution. It indicates reduced engine efficiency.

This exhaust smoke may be reduced by adding suitable additives to thefuel. Especially effective additives are certain cyclopentadienylmanganese tricarbonyls, such as (methylcyclopentadienyl)manganesetricarbonyl. US. 2,818,417 provides a thorough list of useful compoundsof this type, and includes methods of preparing them. Although use ofthese manganese additives substantially reduces the exhaust smoke, asecondary problem may arise in some instances. On combustion of the fuelcontaining the manganese compound, manganese containing deposits areformed on the engine surface which are contacted by the exhaustproducts. As with many engine deposits, an effective method of removingthese manganese containing deposits is desirable.

SUMMARY OF THE INVENTION DESCRIPTION OF THE PREFERRED EMBODIMENTS Anembodiment of this invention is a method of removing manganesecontaining deposits formed on the surfaces of a jet engine from burninga fuel containing a smoke reducing quantity of a cyclopentadienylmanganese tricarbonyl having up to 17 carbon atoms, which comprisestreating said surfaces with an aqueous solution of a salt ofhydroxylamine and an organic acid having up to 18 carbon atoms.

Another embodiment of said method comprises treating the manganesecontaining deposit coated surface with an ice aqueous solutioncontaining up to about 20 percent by weight of the hydroxylaminecompounds described above.

In a preferred embodiment the acid portion of the hydroxylamine salt isderived from an organic acid selected from hydrocarbon, alkyl monoanddicarboxylic acids. The total number of carbon atoms in said organicacids ranges from two to about 18 carbon atoms. In a more pre ferredembodiment, said organic acids have from 2 to 8 carbon atoms. A mostpreferred embodiment utilizes the salt of hydroxylamine and oxalic acid.

Manganese compounds which are useful as smoke reducers in jet fuels arecyclopentadienyl manganese tricarbonyls having the formula wherein R isa cyclopentadienyl hydrocarbon radical having from 5 to 17 carbon atoms.U.S. 2,818,417, issued Dec. 31, 1957, contains an extensive disclosureof the type of manganese compounds which are useful. This listing ofcompounds is incorporated by reference.

(Methylcyclopentadienyl)manganese tricarbonyl is an especially effectivesmoke reducer.

The concentration of the manganese tricarbonyl in the jet fuel may bevaried. Concentrations from 0.025 to about 6.45 grams of manganese pergallon as a cyclopentadienyl manganese tricarbonyl are useful.

By jet fuels, we include distillate hydrocarbons and blends which areuseful as fuel for jet engines. These fuels are principally hydrocarbondistillates heavier than gasoline. In other words they are distillatehydrocarbon fuels having a higher end point than gasoline. They aregenerally composed of distillate fuels and naphtha and blends of theabove, including blends with light hydrocarbon fractions. The end pointof preferable jet fuels is at least 435 F. and more preferably greaterthan 470 F.

Typical jet fuels include JP-3, a mixture of about 70 percent gasolineand 30 percent light distillate having a percent evaporation point of470 F.; JP-4, a mixture of about 65 percent gasoline and 35 percentlight distillate especially designed for high altitude performalrlice;JP-S, an especially fractionated kerosene and the l' e.

The manganese containing deposit which is formed on the jet enginesurfaces comprises a mixture of compounds. Principal components of thismixture are the oxides such as Mn O and Mn O Organic acids which areuseful to prepare hydroxylamine salts suitable for the present inventionmay contain the carboxyl group, the sulfonic acid functional group, thephosphonic acid functional group, the phosphoric acid functional group,and the like. The carboxylic acids, that is, acids containing carboxylfunctional groups include monocarboxylic acids and dicarboxylic acids.These carboxylic acids may contain other substituents besides carbon,hydrogen and the carboxyl group, such as for example, hydroxy groups,halogens and the like. Examples of some useful carboxylic acids aretrichloroacetic acid, abromopropionic acid, 4-hydroxy hexanoic acid,decenoic acid, m-nitrobenzoic acid, glycolic acid, sebacic acid, oleicacid, cyanoacetic acid, cyclohexene carboxylic acid, and the like.

Preferred carboxylic acids are hydrocarbon, alkyl, monoand dicarboxylicacids having from 2 to 18 carbon atoms. Preferred monocarboxylic acidsare propionic acid, stearic acid, dodecanoic acid, 2-ethylhexanoic acid,butanoic acid, 2,4,4-trimethylpentanoic acid, trimethylacetic acid,undecanoic acid, tetradecanoic acid and the like. Preferred dicarboxylicacids are tetradecenedioic acid, octadecanedioic acid, nonanedioic acid,undecanedioic acid, sebacic acid and the like. More preferred carboxylicacids are those having from 2 to about 8 carbon atoms. They areexemplified by acetic acid, octanoic acid, iso- 3 butyric acid,pentanoic acid, adipic acid, suberic acid, malonic acid, glutaric acid,pimelic acid and the like. A most preferred carboxylic acid is oxalicacid.

Sulfonic acids which are useful include the alkyl as well as the benzeneand alkyl benzene sulfonic acids. Examples of useful sulfonic acids aredodecylbenzene sulfonic acid, benzene sulfonic acid, l-octane sulfonicacid, Z-propane sulfonic acid, 2-octadecane sulfonic acid,l-(4,6-dimethyl) heptane sulfonic acid, p-toluene sulfonic acid and thelike. Phosphorus containing organic acids are also useful. Examples ofthese phosphorus containing acids are methyl phosphonic acid, octyldihydrogen phosphate, phenyl phosphonic acid, butyldecylhydrogenphosphate, octadecyl phosphonic acid, dodecyl dihydrogen phosphate, andthe like.

Although salts of hydroxylamine and strong mineral acids such assulfuric acid also remove manganese deposits, they are not as effectiveas the salts of the preferred organic acids. Data will be presentedbelow illustrating the greater effectiveness of the organic acidhydroxylamine salts.

Hydroxylamine salts useful in this invention include fully neutralizedsalts and partially neutralized salts. A fully neutralized salt is onein which one molecule of hydroxylamine is provided for each acidhydrogen in the acid molecule. Thus, salts of hydroxylamine and adipicacid can be prepared which contain (1) one mole of hydroxylamine and onemole of adipic acid or (2) two moles of hydroxylamine and one mole ofadipic acid [(H NOH) -HOOC(CH )4COOH]. The former salt is partiallyneutralized, while the latter salt is fully neutralized. Only acidshaving more than one acid hydrogen can form partially neutralized salts.A preferred partially neutralized salt is the salt of one mole ofhydroxylamine and one mole of oxalic acid.

The concentrations of hydroxylamine salts which are used in the presentproces may be varied. In general, concentrations of from about 0.001percent to about 20 percent by weight are useful. Saturated solutionsare especially useful.

An outstanding feature of the present invention is that it offers amethod of removing manganese containing deposits in a jet engine withoutrequiring its disassembly or its removal from its mounting. Thus, theengine can be cleaned while it is still in place in an airplane fuselagefor example, by simply spraying the solution of hydroxylamine saltdescribed above, through the engine, while the engine is being cranked.Cranking a jet engine means that the engine is turning but the fuel isnot ignited. By cranking the engine, all the engine surfaces which mayhave a manganese containing deposit become exposed to the spray.

Another method of spraying the solution into the jet engine is to feedit through the fuel feed system between the fuel tank and the combustionarea. Using this procedure, the solution will contact only those enginesurfaces on which the fuel and exhaust products would impinge. Theengine is cranked to insure better contact. In either case, the spraymay be continuously recycled if desired, to reduce the volume ofsolution required. Besides the spraying technique, the engine can becleaned by immersing it in a suitably designed vessel containing theacid/hydroxyl amine compound solution for a period of time sufficient todissolve the manganese containing deposits. After such an immersion orafter a spray treatment, the engine is generally rinsed with a purewater. A combination of the spray-soak procedure can also be used.

The engine treatment can be carried out either before or after theengine has cooled after being in operation. The solution with which thetreatment is carried out may also be warmed, if desired. By treating theengine while hot or by using a hot solution, treatment time to clean theengine can be reduced. Heating either the engine surfaces or thesolution, however, is not required. Whatever means is used to carry outthe engine treatment, the only requirement is that a solution, as hereindescribed contact the manganese containing deposits on the enginesurfaces.

The effectiveness of the aqueous solution of hydroxylamine salttreatment was determined in a laboratory procedure using a metal testspecimen on which was deposited a manganese-containing deposit. The testspeciment was prepared by allowing the exhaust stream from burning a jetfuel containing about 0.1 volume percent (1.29 g./gal. of manganese) of(methylcyclopentadienyl) manganese tricarbonyl, to impinge on the metalpiece. The manganese containing deposit appeared as a brownish depositon the metal surface. This test specimen was then placed in a chamberwhere it was subjected to an alternate spray/soak treatment. Thistreatment consists of (a) spraying (1.48 gal. per hour at 10 p.s.i.g.)the test piece with the test solution for five minutes while the testpiece is spinning and (b) then allowing the wet specimen to set for anadditional five minutes; this spray/soak cycle is repeated three times.At the end of the treatment cycle, the test piece is rinsed with clearwater and is then allowed to dry. The treated test piece is thenweighed. The loss in deposit weight (the amount of deposit dissolved) isrecorded as percent deposit loss.

Aqueous solutions of hydroxylamine sulfate (for comparison) andhydroxylamine oxalate (one mole hydroxylamine: one mole oxalic acid),where evaluated using this spray/soak test procedure. The data obtainedis presented in the following table. All percentages are by weight.

TABLE l.--DEPOSIT REMOVAL IN SPRAY/SOAK Percent Test Mn consolutiontaining temperadeposit Test solution ture removed Water R.I. 0 Waterplus 10 percent (HgNHOh- HZSO; R.T. 31 Water plus 10 percentH2NOHHO0CCOOH R.'I. 46

1 R.T.= Room temperature.

The data in Table 1 shows that the solution removes 46% of the manganesecontaining deposit whereas the (H NOH) -H SO solution removes only 31%of the deposit.

Similar deposit removal is obtained using any of the following aqueoussolutions instead of the (7) 4% solution of salt of H NOH andbenzenesulfonic acid (8) 6% solution of H NOH-Cl CCOOH (9) 1.5% solutionof salt of H NOH and octyl phosphonic acid.

The results presented above clearly demonstrate that the manganesecontaining deposits formed on jet engine parts can be very effectivelyremoved by treatment with an aqueous solution of a hydroxylamine salt ofan organic acid as herein described. The manganese containing deposithas been described as that being formed from burning jet fuel containinga cyclopentadienyl manganese tri- 5 carbonyl. However, it is consideredwithin the scope of the present invention that the present method willbe effective for removing manganese containing deposits obtained onburning jet fuel containing other manganese bearing additives.

The process of the present invention is described above. It is intendedthat the present invention be limited only within the lawful scope andextent of the following claims.

What is claimed is:

1. A method of removing manganese containing deposits formed on surfacesof a jet engine from burning a fuel containing a cycyopentadienylmanganese tricarbonyl compound, wherein the cyclopentadienyl radical hasup to 17 carbon atoms, which comprises treating said surfaces with anaqueous solution of a salt of hydroxylamine and an organic acid havingfrom 2 to about 18 carbon atoms selected from the group consisting of(a) hydrocarbon alkyl carboxylic acids containing up to two carboxylgroups,

(b) alkyl and aryl sulfonic acids,

(0) alkyl and aryl phosphonic acids, and

(d) alkyl phosphoric acids.

2. The method of claim 1 wherein said cyclopentadienyl manganesetricarbonyl is (methylcyclopentadienyl) manganese tricarbonyl at aconcentration in said fuel of from 0.025 to about 6.45 grams ofmanganese per gallon.

3. The method of claim 2 wherein said aqueous solution contains from0.001% to about 20% by weight of said hydroxylamine salt,

4. The method of claim 1 wherein said aqueous solution contains from0.001% to about 20% by weight of said hydroxylamine salt.

5. The method of claim 4 wherein said acid is a hydrocarbon alkylcarboxylic acid having from 2 to about 18 carbon atoms.

6. The method of claim 4 wherein said acid is a hydrocarbon alkylcarboxylic acid having from 2 to about 8 carbon atoms.

7. The method of claim 6 wherein said acid is a dicarboxylic acid.

8. The method of claim 7 wherein said acid is oxalic acid.

9. The method of claim 8 wherein said salt is H NOH-HOOCCOOH.

10. The method of claim 9 wherein said fuel contains about 1.29 gramsper gallon of manganese as (methylcyclopentadienyl)manganese tricarbonyland said aqueous solution contains 10% by weight of said salt.

References Cited UNITED STATES PATENTS 2,992,995 7/1961 Arden -L 13420X3,003,970 10/1961 Call 1342X 3,025,189 3/1962 Arden 1343 3,216,85711/1965 Duvall.

MORRIS O. WOLK, Primary Examiner J. T. ZATARGA, Assistant Examiner US.Cl. X.R. l3422, 42

